{"id":36726,"date":"2025-10-08T15:11:22","date_gmt":"2025-10-08T14:11:22","guid":{"rendered":"https:\/\/www.vtei.cz\/2025\/10\/rozhovor-s-ing-liborem-ellederem-ph-d-hydrologem-z-ceskeho-hydrometeorologickeho-ustavu-v-praze-2\/"},"modified":"2025-10-08T19:46:52","modified_gmt":"2025-10-08T18:46:52","slug":"rozhovor-s-ing-liborem-ellederem-ph-d-hydrologem-z-ceskeho-hydrometeorologickeho-ustavu-v-praze-2","status":"publish","type":"post","link":"https:\/\/www.vtei.cz\/en\/2025\/10\/rozhovor-s-ing-liborem-ellederem-ph-d-hydrologem-z-ceskeho-hydrometeorologickeho-ustavu-v-praze-2\/","title":{"rendered":"Interview with Ing. Libor Elleder,\u00a0Ph.D., hydrologist from the\u00a0Czech Hydrometeorological Institute, Prague"},"content":{"rendered":"\"\"<\/a>\n

Have you ever wondered what a\u00a0hydrologist might discuss at a\u00a0table with historians, archivists, and chroniclers? Can historical data help us gain\u00a0a\u00a0better understanding of\u00a0today\u2019s\u00a0flood risk assessment? And might deeper knowledge of\u00a0past floods prepare us for future ones linked to climate change? We put these questions to Ing. Libor Elleder, Ph.D., in\u00a0the\u00a0October hydrology issue of\u00a0VTEI<\/span>.<\/span><\/p>\n

Dr Elleder, in\u00a0your view, what is the\u00a0significance of\u00a0historical sources such as chronicles, old maps, and municipal records for hydrology today?<\/span><\/span><\/h4>\n

To put it simply, all these historical sources significantly expand our knowledge of\u00a0extreme events such as floods, droughts, heavy rainfall, but also harsh winters, tornadoes, or crop failures, reaching far back into the\u00a0past, beyond the\u00a0reach of\u00a0any instrumental records based on measurements of\u00a0temperature, precipitation, or water levels. It is not just about the\u00a0intensity or magnitude of\u00a0floods, but also their typical seasonality, which can change gradually over time due to climatic conditions. These are just a\u00a0few examples. Should we simply give up on such information? That might be the\u00a0defence of\u00a0historical sources. But why are such sources not generally accepted in\u00a0hydrology? An impartial judge might raise that question. Were the\u00a0prosecution to speak, we would probably hear about the\u00a0vagueness, inaccuracy, unreliability, and \u201cgaps\u201d in\u00a0historical sources. The\u00a0devil\u2019s\u00a0advocate would add that chroniclers often embellished their accounts, lacked impartiality, flood markers were moved, watercourses altered, natural conditions changed, and everything is simply different now, so such sources are useless. A\u00a0member of\u00a0the\u00a0jury might also add that they had never even heard of\u00a0anything like historical sources and that it is better to stick to \u201ctraditional\u201d methods. The\u00a0usefulness of\u00a0these sources therefore needs to be carefully explained and patiently defended. It seems, however, that it is not only chronicles that are at risk of\u00a0being forgotten, but also the\u00a0records and documents created and preserved by generations of\u00a0water management professionals fifty or a\u00a0hundred years ago. The\u00a0political upheavals of\u00a0the\u00a0twentieth century, combined with generational forgetfulness, have also deprived us of\u00a0many more recent, equally irreplaceable sources.<\/span><\/p>\n

Zlata \u0160\u00e1malov\u00e1 from the\u00a0Elbe Basin\u00a0State Administration recently recalled how, decades ago, water management archives were being destroyed, piled onto a\u00a0large heap. At the\u00a0last moment, however, it was possible to rescue some bridge projects, river engineering plans, and riverside maps, preserving them for the\u00a0future. From the\u00a0archives of\u00a0the\u00a0Sewerage Commission, most of\u00a0the\u00a0glass negatives documenting water management structures from the\u00a0early twentieth century were reportedly sent to glassworks for melting. Even so, many were saved, including an entire truckload of\u00a0these glass negatives. After all, water management and hydrology archives and documents form part of\u00a0historical hydrology. It has been more than half a\u00a0century, but it is important to mention.<\/span><\/p>\n

Do you ever encounter doubts about the\u00a0reliability of\u00a0such sources?<\/span><\/span><\/h4>\n

In the nearly forty years I have worked in hydrology, I have met many colleagues who were somewhat sceptical about combining hydrology with history or other humanities disciplines; however, the reverse is also true. Others were enthusiastic.\u00a0<\/span>It depends on one\u2019s\u00a0character, personal experience, and upbringing. My parents had a\u00a0humanities education: my mother studied at the\u00a0Faculty of\u00a0Arts and worked at the\u00a0Technical Museum in\u00a0Prague, while my father was a\u00a0lawyer whose favourite hobby was history. So our home library was full of\u00a0books on history and art, and, alongside politics, these were frequent topics of\u00a0discussion. When I\u00a0visited my mother at the\u00a0Technical Museum, I\u00a0felt very comfortable, or even great, among the\u00a0old machines, drawings, and maps. One more explanatory note: my strong appreciation for visual art. Old maps, manuscripts, and books are stunningly beautiful, there is no question about that. What I\u00a0want to emphasise is that historical sources never repelled me; quite the\u00a0opposite.<\/span><\/p>\n

The\u00a0question, however, is how all these sources can actually be used, say, in\u00a0hydrology. My grandfather came from the\u00a0ancient Ille milling family in\u00a0South Bohemia. At his family mill in\u00a0Kosteln\u00ed Radou\u0148, there were two beautifully marked flood gauges from the\u00a0flash floods of\u00a01934 and 1949. I\u00a0assumed that, just as there were floodmarks at our family mill, similar floodmarks could be found at other mills. Later, I\u00a0realised that this was not quite the\u00a0case. In\u00a0theory, such data harbour vast informational potential. For me, they were a\u00a0powerful initial source of\u00a0inspiration.<\/span><\/p>\n

The\u00a0database of\u00a0Czech watermills compiled by Rudolf \u0160imek now contains 11,904\u00a0mills. That is a\u00a0substantial number, and if flood records had survived, they would be an invaluable resource \u2013 especially for smaller catchments, where no systematic records exist. Each mill would have had a\u00a0flood gauge and some form of\u00a0water-level measurement. It is almost certain\u00a0that, at one time, most mills had at least some flood marks. However, a\u00a0field survey in\u00a02007 revealed that in\u00a0most cases these marks were in\u00a0a\u00a0very poor state, even at sites where they had still been visible around 1930. The\u00a0authors of\u00a0longitudinal profiles at the\u00a0Hydrological Institute recorded a\u00a0number of\u00a0such water levels in\u00a0the\u00a0Vltava, S\u00e1zava, Jizera, and Berounka rivers between 1920 and 1950. One can see that, on the\u00a0Vltava before the\u00a0cascade dams were built, profiles with one or more flood marks existed at almost every, or at least every second, river kilometre.<\/span><\/p>\n

How can chronicles and municipal records be utilised?<\/span><\/span><\/h4>\n

A\u00a0similar situation applies to chronicles and municipal records. Today, there are over 6,200\u00a0municipalities in\u00a0the\u00a0Czech Republic, many of\u00a0which disappeared after the\u00a0war, so the\u00a0actual number was even higher. Again, this represents an enormous amount of\u00a0potential data on weather and floods. Working with them does not always lead automatically to success; however, when we were analysing the\u00a0floods of\u00a0Rakovnick\u00fd stream, a\u00a0case occurred of\u00a0two alternative dates for a\u00a0flood on the\u00a0Rakovnick\u00fd and Li\u0161ansk\u00fd streams. I\u00a0then found an explanation in\u00a0the\u00a0chronicle of\u00a0the\u00a0village of\u00a0H\u0159edle. In\u00a0May and June 1852, the\u00a0village was struck by a\u00a0total of\u00a0five flash floods within\u00a0a\u00a0period of\u00a0about three weeks. Both alternatives were confirmed, and moreover we obtained information on a\u00a0longer period during which flash floods affected a\u00a0broader area. The\u00a0use of\u00a0a\u00a0large number of\u00a0municipal chronicles also showed that May floods in\u00a0the\u00a0Rakovn\u00edk, Podbo\u0159any, and Beroun regions are by no means exceptional, but rather something typical. The\u00a0great flood of\u00a025\u00a0May 1872 fits into the\u00a0context of\u00a0this area quite well. From 1836, all market towns were required to keep chronicles, and a\u00a0hundred years later, this applied to all municipalities. It seems that these records of\u00a0floods, droughts, and storms in\u00a0local chronicles have largely been left unused.<\/span><\/p>\n

And how far into the\u00a0past can one look by means of\u00a0these sources?<\/span><\/span><\/h4>\n

Going further back, written sources related to the\u00a0history of\u00a0royal or dependent towns can be consulted, with records beginning in\u00a0the\u00a0fifteenth or sixteenth century. In\u00a0Prague, evidence of\u00a0floods starts with Kosmas\u2019s\u00a0chronicle; the\u00a0earliest flood mentioned here occurred in\u00a0September 1118.<\/span><\/p>\n

Our oldest riverside maps date from the\u00a0reign of\u00a0Maria Theresa and her sons Joseph II and Leopold II, mainly from the\u00a0period 1770 to 1795. The\u00a0oldest map of\u00a0the\u00a0Otava showing water depths in\u00a0cross-sections is from 1794, while the\u00a0earliest such map of\u00a0the\u00a0Vltava is from around 1822 to 1825. What use are these materials? They are the\u00a0only records we have of\u00a0natural or human-induced changes in\u00a0our rivers. They provide answers to questions such as the\u00a0causes behind the\u00a0separation of\u00a0certain\u00a0river meanders or the\u00a0changes in\u00a0the\u00a0cross-profiles of\u00a0the\u00a0Vltava and the\u00a0Elbe.<\/span><\/p>\n

From 10 to 12\u00a0September 2025, the\u00a0third international workshop of\u00a0the\u00a0Flood Working Group (FWG) of\u00a0PAGES (Past Global Changes) was held in\u00a0Prague. The\u00a0group aims to create a\u00a0global database of\u00a0flood event records. It was established in\u00a02016 at the\u00a0first workshop held at the\u00a0University of\u00a0Grenoble. Efforts to combine methods of\u00a0historical hydrology with the\u00a0results of\u00a0paleoflood hydrology are still developing. We were pleased that this year Czechia was represented by a\u00a0key speaker, Associate Professor Jan Hradeck\u00fd from the\u00a0University of\u00a0Ostrava, an expert in\u00a0river morphology and the\u00a0documentation of\u00a0contemporary and past landslides. Thanks to the\u00a0archaeologist Jan Havrda, we were also able to show some dated fluvial layers in\u00a0Prague, even from the\u00a014th century, when the\u00a0frequency of\u00a0major floods was exceptionally high according to documentary sources. A\u00a0great support and model in\u00a0this regard are experts from the\u00a0USA, the\u00a0United Kingdom, Switzerland, Spain, Germany, the\u00a0Netherlands, and Israel.<\/span><\/p>\n

Can you give a specific example where historical sources have yielded something interesting, new, or exceptionally useful?<\/span><\/span><\/h4>\n

Recently, a\u00a01714\u00a0map of\u00a0the\u00a0Brand\u00fds and Nymburk manorial estates was discovered in\u00a0a\u00a0Viennese archive, showing the\u00a0actual confluence of\u00a0the\u00a0Elbe and Jizera rivers up to Star\u00e1 Boleslav. It includes mill race channels, vanished fishponds, and other features. In\u00a0the\u00a01844 riverside maps of\u00a0the\u00a0Elbe, water depths, shallows, and stones, removed from the\u00a0riverbed in\u00a0the\u00a0nineteenth century, are recorded.<\/span><\/p>\n

In\u00a0the\u00a01990s in\u00a0our archive in\u00a0Brozany, we discovered the\u00a0oldest series of\u00a0daily records from Magdeburg, beginning in\u00a01727. It is possibly the\u00a0longest series of\u00a0daily water levels in\u00a0Europe, or even in\u00a0the\u00a0world. For a\u00a0long time, no one knew about it. Around 1880, Professor A. R. Harlacher, head of\u00a0the\u00a0Hydrometric Section of\u00a0the\u00a0Hydrographic Commission of\u00a0the\u00a0Kingdom of\u00a0Bohemia, had it sent to him by colleagues in\u00a0Magdeburg, as he was interested in\u00a0the\u00a0declining trends of\u00a0minimum water levels in\u00a0this old record. Had the\u00a0package of\u00a0extracts been lost, no one would have noticed or missed it. However, as we have it, it is much better. Many similar series are considered lost, at least for the\u00a0time being. This example gives hope that many more may still be found in\u00a0various uncatalogued collections \u2013 perhaps in\u00a0places we would not expect. My colleague Jan \u0158i\u010dica copied the\u00a0package and sent it back to German colleagues in\u00a0Magdeburg, returning it after 110 years. We divided the\u00a0work of\u00a0transcribing the\u00a0series between the\u00a0Czech Hydrometeorological Institute (CHMI) and TGM WRI equally with Ladislav Ka\u0161p\u00e1rek; he did not need convincing that it was a\u00a0good idea. Today, colleagues from the\u00a0German research institute Bundesanstalt f\u00fcr Gew\u00e4sserkunde (BfG) have already published two studies on changes in\u00a0the\u00a0Magdeburg gauge profile, including a\u00a0quantification of\u00a0this unique flow series.<\/span><\/p>\n

And what do these discoveries tell us about the\u00a0actual development of\u00a0water management?<\/span><\/span><\/h4>\n

It is not only about floods. It is quite logical, and probably even necessary, to attempt to understand the\u00a0development of\u00a0water management as a\u00a0discipline. Only with the\u00a0insights gained from the\u00a0commission inspections of\u00a0the\u00a0Elbe from M\u011bln\u00edk to Cuxhaven did new information clearly emerge, for example regarding the\u00a0significance of\u00a0\u201chunger stones\u201d and the\u00a0markings on them. Their importance was clear to the\u00a0commissioners at the\u00a0time. When studying floods and droughts, we also need to consider the\u00a0historical development of\u00a0settlement along the\u00a0rivers. Twenty years ago, under the\u00a0leadership of\u00a0Rudolf Br\u00e1zdil, the\u00a0book Historical and Recent Floods<\/span> was published. Since then, we have gathered a wealth of information on both floods and the development of Prague and other settlements. This allows us to answer questions such as whether floods similar to those of 1997 or 2002 occurred in the past, with far greater certainty than before. In our country, we are fortunate to have relatively long, systematically\u00a0<\/span>measured series of\u00a0water levels and precipitation, largely thanks to the\u00a0foresight and expertise of\u00a0Professors A. R. Harlacher and F. J. Studni\u010dka. However, if we look at the\u00a0history of\u00a0floods on major rivers such as the\u00a0S\u00e1zava, Oh\u0159e, Jihlava, Dyje, and even the\u00a0Jizera, we see that the\u00a0recorded series only begin\u00a0after the\u00a0era of\u00a0major floods in\u00a01784, 1845, and 1862. Without this insight, we would probably obtain\u00a0a\u00a0rather distorted picture of\u00a0major floods in\u00a0these and other catchments. And this is just one example.<\/span><\/p>\n

Could you give a specific example of\u00a0when historical records have helped to better understand or refine flood risk assessment?<\/span><\/span><\/h4>\n

Perhaps the\u00a0question could be framed the\u00a0other way around: when has the\u00a0absence of\u00a0historical data led to mistakes and worsened disasters? Such examples are often cited in\u00a0lectures by key speakers, for instance Victor Baker from the\u00a0University of\u00a0Arizona, or arguably Spain\u2019s\u00a0leading expert in\u00a0paleoflood hydrology, Gerard Benito. I\u00a0will give just two examples, both connected to the\u00a0year 2011. Coincidentally, both involved nuclear power stations threatened by water. In\u00a0March of\u00a0that year, it was Japan\u2019s\u00a0Fukushima Daiichi, endangered by an earthquake and the\u00a0resulting tsunami. In\u00a0June, the\u00a0Fort Calhoun plant on the\u00a0Missouri River faced serious flooding. In\u00a0both cases, historical data are available; it is just not very clear why they were not properly used in\u00a0the\u00a0design of\u00a0the\u00a0structures. Although the\u00a0US power station was inundated, the\u00a0event passed without major consequences; however, five years later the\u00a0plant was decommissioned and gradually dismantled. In\u00a0Japan, the\u00a0outcome was much worse, as is widely known.<\/span><\/p>\n

How did the\u00a0scientific community view the\u00a0use of\u00a0historical records in\u00a0the\u00a0past?<\/span><\/span><\/h4>\n

Professor Nobuo Shuto of\u00a0Tohoku University has studied tsunamis, both through modelling and historical cases. As he recalled, a\u00a0key event for him was the\u00a0great tsunami of\u00a01983. Eyewitnesses during his field research told him that, while it was terrible, it was nothing compared to the\u00a0tsunami of\u00a01896. He then began studying historical cases; however, by that time, the\u00a0Fukushima Daiichi plant had already been built.<\/span><\/p>\n

It is quite interesting that it was precisely in\u00a0the\u00a01980s that there was a\u00a0general return to the\u00a0use of\u00a0historical data. Even then, a\u00a0number of\u00a0papers appeared, including the\u00a01982 Science<\/span> article Palaeoflood Hydrology<\/span> by V. R. Baker. The\u00a0theoretical basis for incorporating unsystematic data into statistical analyses came with formulas published in\u00a01987 by J. R. Stedinger and T. A. Cohn, which allow datasets above a\u00a0chosen threshold (including pre-instrumental data) to be combined with annual maximum series. At the\u00a0same time, V\u00edt Kleme\u0161 published several articles criticising the\u00a0derivation of\u00a0flood recurrence intervals from very short records. Kleme\u0161 emigrated to Canada in\u00a01968, where he became a\u00a0recognised hydrologist. I\u00a0remember lectures by V.\u00a0R.\u00a0Baker, who particularly highlighted Kleme\u0161 and endorsed his ideas. When Ladislav Ka\u0161p\u00e1rek and I\u00a0were preparing for this year\u2019s\u00a0lecture on 18\u00a0March, marking the\u00a0release of\u00a0the\u00a0book Historical Floods on the\u00a0Rakovnick\u00fd Stream<\/span>, he recalled that in\u00a0the\u00a01980s, these very Kleme\u0161 articles were the\u00a0ones he read and knew well.<\/span><\/p>\n

I\u00a0was not present when Ladislav Ka\u0161p\u00e1rek discovered, during fieldwork after the\u00a0July 1981 flood, a\u00a0flood mark from 1872 on the\u00a0rock above \u010cerven\u00fd Stream. He recalled this repeatedly, most recently during the\u00a0aforementioned lecture this year. In\u00a01984, he published a\u00a0paper explicitly addressing the\u00a0influence of\u00a0incorporating historical data into statistical analyses. Today, the\u00a0peak values of\u00a0the\u00a0Litavka and Berounka rivers in\u00a01872 are taken for granted. However, this was by no means obvious: the\u00a0reconstruction of\u00a0the\u00a0flood on the\u00a0Litavka was somewhat daring, and publishing the\u00a0results was bold.<\/span><\/p>\n

Can we find other personalities who similarly emphasized the\u00a0importance of\u00a0historical floods?<\/span><\/span><\/h4>\n

There is a certain parallel here with the Japanese Professor Shuto and his field survey after the 1983 tsunami, which set him on the path toward studying historical events. Since 1978, historian and archivist Ji\u0159\u00ed Kyn\u010dil had been working on excerpts\u00a0<\/span>concerning historical floods in the Ore Mountains and the Oh\u0159e River Basin. He carried out this work for the state enterprise Povod\u00ed Oh\u0159e. At the time, the focus was on coal mining in the region and the future protection of surface mines. It was necessary to gather as much information as possible on floods in the short Ore Mountain tributaries of the B\u00edlina and Oh\u0159e rivers. Less well known is a shorter publication on the J\u00edlovsk\u00fd Stream. As early as 1983, Ji\u0159\u00ed Kyn\u010dil noted that estimates of flood recurrence intervals for the J\u00edlovsk\u00fd Stream were probably underestimated. It is interesting to read, in the reflections of a person with a humanities background, the same objections regarding the insufficiency of thirty- or fifty-year records for deriving a\u00a0100-year flow as those raised by world-leading hydrologist V\u00edt Kleme\u0161; the\u00a0documented floods from 1897 and 1927\u00a0had not been used. Shortly afterwards, an actual extreme flood occurred on the\u00a0J\u00edlovsk\u00fd Stream, which Ladislav Ka\u0161p\u00e1rek then analysed. This is how the\u00a0two of\u00a0them became connected through the\u00a0J\u00edlovsk\u00fd Stream. Ji\u0159\u00ed Kyn\u010dil later inspired Old\u0159ich Kotyza, an archaeologist from Litom\u011b\u0159ice, to explore the\u00a0topic of\u00a0historical floods \u2013 a\u00a0subject Kotyza dedicated his entire life to, alongside climate history. Ladislav Ka\u0161p\u00e1rek believed that estimates of\u00a0extreme flows were crucial. In\u00a0addition to his estimates for the\u00a0Litavka flood of\u00a01872, he provided estimates for the\u00a0St\u0159ela, Bl\u0161anka, Berounka, Vltava, and finally the\u00a0Rakovnick\u00fd Stream. In\u00a0doing so, he made a\u00a0substantial contribution to our understanding of\u00a0potential flood risk.<\/span><\/p>\n

How do you verify and interpret historical data, which often appear not as precise figures but as descriptions or narratives?<\/span><\/span><\/h4>\n

There are several considerations. We consider contemporary accounts (primary rather than secondary sources) to be the\u00a0most reliable. We also give preference to quantitative data, which usually concern historical peak water levels. Typically, these are flood marks, so-called epigraphic sources. Equally precise can be flood heights derived from chronicle entries linked to fixed reference points. The\u00a0best-known example is the\u00a0Gothic sculpture of\u00a0\u201cBrad\u00e1\u010d\u201d (Bearded Man) in\u00a0Prague. We surveyed it in\u00a02004, which resolved doubts about the\u00a0circumstances of\u00a0its relocation to a\u00a0new position in\u00a01848. In\u00a0this way, we now have a\u00a0series of\u00a0quite precise peak water levels in\u00a0Prague dating back to 1481.<\/span><\/p>\n

It could also be the\u00a0floor level of\u00a0a\u00a0church. However, there can always be obstacles and uncertainties about past changes in\u00a0the\u00a0position of\u00a0such a\u00a0site or structure. A\u00a0sad example is the\u00a0Church of\u00a0St. Anne in\u00a0Hradec Kr\u00e1lov\u00e9, which was demolished during the\u00a0construction of\u00a0fortifications around 1775. A\u00a0building plan of\u00a0the\u00a0church survives, but without elevations. In\u00a0the\u00a0sixteenth and seventeenth centuries, flood heights on the\u00a0Elbe were repeatedly referenced to the\u00a0floor level of\u00a0this church. This allows us to know the\u00a0relative levels of\u00a0these peaks quite precisely. Yet linking this series to other extreme floods such as the\u00a0devastating flood of\u00a01775 or probably the\u00a0worst floods in\u00a01804 and 1846 remains a\u00a0problem. I\u00a0remember being shown around Hradec Kr\u00e1lov\u00e9 by the\u00a0aforementioned Zlata \u0160\u00e1malov\u00e1, who sadly pointed out the\u00a0area around the\u00a0roundabout, where perhaps some tiny remnants of\u00a0the\u00a0church still lie buried underground.<\/span><\/p>\n

What should be done in\u00a0cases where only imprecise or qualitative descriptions of\u00a0floods are available?<\/span><\/span><\/h4>\n

There are many floods where the\u00a0determination of\u00a0peak water levels is somewhat \u201cfuzzy\u201d or where we only have records of\u00a0significant property damage, giving us a\u00a0\u201cqualitative\u201d description, such as damage to crops, objects being swept away, houses damaged, or bridges destroyed. A\u00a01-to-3 point scale is used here, with an approximate relation to N<\/span>-year return periods provided as a\u00a0guide. Clearly, if people are taking refuge on rooftops, and houses and bridges are collapsing, it is not going to be a\u00a05-year flood, or even a\u00a020-year one. In\u00a0such cases, we either settle for an estimate or rely on a\u00a0better-documented situation further downstream, where quantitative data can serve as a\u00a0reference. It is important to emphasise that historical hydrology is not just the\u00a0collection of\u00a0flood data. One must also understand the\u00a0development of\u00a0a\u00a0given locality over time, including any changes in\u00a0the\u00a0floodplain\u00a0and the\u00a0river channel. This can sometimes be quite challenging.<\/span><\/p>\n

\"\"<\/a>A photo of\u00a0Bearded man (or in\u00a0Czech \u201cBrad\u00e1\u010d\u201d) from a 2004 survey shows that his head is, in\u00a0contrast with mine, 70 cm tall<\/h6>\n

Can you provide a specific example where knowledge of\u00a0the\u00a0development of\u00a0a locality helped to correctly interpret a flood?<\/span><\/span><\/h4>\n

One of\u00a0the\u00a0best examples is Prague. Here, since the\u00a0construction of\u00a0weirs (roughly from the\u00a0thirteenth and fourteenth centuries) the\u00a0riverbed did not deepen, in\u00a0contrast with, for instance, in\u00a0Cologne, Germany. Here, the\u00a0Rhine gradually deepened its channel, influenced in\u00a0part by various human interventions. Evidence of\u00a0this was left in\u00a0the\u00a0form of\u00a0drawings of\u00a0German towns during his voyage along the\u00a0Rhine, Main, and Danube in\u00a01636 by the\u00a0Czech etcher V\u00e1clav Hollar. Weirs extending across the\u00a0entire river were by no means common on larger rivers in\u00a0the\u00a0Middle Ages and often are not today. Mills managed without them, and on the\u00a0Rhine, boat mills were more typical; constructing a\u00a0stone bridge across a\u00a0river was generally feasible only on smaller streams in\u00a0the\u00a0medieval period. The\u00a0Vltava in\u00a0Prague, the\u00a0Elbe in\u00a0Dresden, and the\u00a0upper Danube in\u00a0Regensburg remained, for a\u00a0long time (roughly until the\u00a0nineteenth century) at the\u00a0limits of\u00a0technical possibility. On the\u00a0Rhine, floating bridges were often used, for example in\u00a0Mannheim. The\u00a0situation in\u00a0Prague is actually quite unique; riverbed changes were slowed by the\u00a0system of\u00a0weirs, and alterations in\u00a0terrain\u00a0heights were halted by the\u00a0gradual paving of\u00a0the\u00a0city, a\u00a0process that began in\u00a0the\u00a0thirteenth and fourteenth century. This knowledge allows us to interpret reports of\u00a0major floods, such as those occurring during the\u00a0construction of\u00a0Charles Bridge. At that time, Prague experienced a\u00a0series of\u00a0floods in\u00a01359, 1367, 1370, and 1374, for which we can estimate peak levels approximately, based on the\u00a0horizontal extent reaching churches such as St. Michael, St. Giles, or St. Linhart. This is why it is important to study in\u00a0detail how the\u00a0Old Town of\u00a0Prague was inundated in\u00a0the\u00a0nineteenth century, when peak water levels are already known with high precision. Such knowledge is invaluable. It allows us to better understand what two prominent chroniclers of\u00a0the\u00a0time of\u00a0Charles IV meant in\u00a0their brief descriptions of\u00a0the\u00a0water reaching the\u00a0Old Town. Put in\u00a0modern terms, they recorded that Prague experienced roughly four \u201c50 to 100-year floods\u201d over a\u00a0fifteen-year period beginning in\u00a01359.<\/span><\/p>\n

How can the\u00a0reliability of\u00a0historical descriptions of\u00a0extreme floods be verified?<\/span><\/span><\/h4>\n

When, as part of a research project on changes in floodplains in 2007, we surveyed the floodmarks along the S\u00e1zava River, we came across reports of a flood in Lede\u010d nad S\u00e1zavou that had reached some two to three metres above the\u00a0Q100\u00a0<\/span>level. This might be dismissed as an unreliable record. Yet similar descriptions of\u00a0flood heights were found in\u00a0every surrounding town, from \u017d\u010f\u00e1r nad S\u00e1zavou to K\u00e1cov. These data were consistent with the\u00a0descriptions of\u00a0the\u00a0number of\u00a0drowned persons in\u00a0the\u00a0respective municipal and parish registers \u2013 in\u00a0total, 240 people drowned. The\u00a0flood in\u00a0question occurred on 31\u00a0July 1714. I\u00a0mention this case because we attempted to reconstruct a\u00a0plausible rainfall scenario that could have produced a\u00a0hydrological response corresponding to at least one chronicle description. The\u00a0rise and fall of\u00a0the\u00a0S\u00e1zava River was in\u00a0detail described by the\u00a0dean of\u00a0the\u00a0church in\u00a0N\u011bmeck\u00fd Brod town (today Havl\u00ed\u010dk\u016fv Brod). The\u00a0required rainfall and its intensity ultimately still \u201cfit\u201d under the\u00a0envelope curve of\u00a0maximum precipitation for our country. It worked!<\/span><\/p>\n

\"\"<\/a><\/span>HEX Conference, Bonn 2014. Participants in\u00a0front of\u00a0the\u00a0Main\u00a0Gate of\u00a0the\u00a0town of\u00a0Eibelstadt, with about 20 to 30 flood marks from 1550 to 2002.<\/h6>\n

In\u00a0what way are historical floods systematically made accessible today?<\/span><\/h4>\n

In\u00a0recent years, we have been working to bring together information on selected extremes into the\u00a0MEF mapping application. MEF is built on ArcGIS. Its purpose is straightforward: to present historical floods in\u00a0their full spatial extent. Major regional summer floods cover hundreds of\u00a0thousands of\u00a0square kilometres, while great winter floods \u2013 such as those in\u00a0February 1374 and 1784 \u2013 affected an extraordinary area stretching from France to Bohemia, possibly even beyond. Processing such events can be time-consuming, but the\u00a0reward lies in\u00a0being able to view each episode as a\u00a0whole and compare it with other historical situations. The\u00a0key motivation here is precisely the\u00a0verification of\u00a0data within\u00a0the\u00a0overall context. An example is the\u00a0February 1374 flood; on Czech territory, we have only two mentions \u2013 from Prague and the\u00a0Oh\u0159e Basin\u00a0\u2013 yet these are confirmed by dozens of\u00a0descriptions across Central and Western Europe. The\u00a0credibility of\u00a0later chronicle records, where more detailed notes survive, is reinforced by matching evidence: for instance, the\u00a0travel times of\u00a0flood waves in\u00a01675, 1784, 1824 or 1890 between towns such as \u010cesk\u00e9 Bud\u011bjovice, Prague, Dresden and Magdeburg, or the\u00a0mutually consistent descriptions of\u00a0damage and peak water levels.<\/p>\n

When researching historical events, do you collaborate with historians, archivists or other experts outside the\u00a0natural sciences?<\/span><\/h4>\n

Over time, I found several colleagues who were either interested in the subject or at least willing to engage with it \u2013 sometimes both. Perhaps the best example was\u00a0the archaeologist Old\u0159ich Kotyza. When, in 1995, he published his booklet Historic Floods on the Lower Elbe and the Vltava on the occasion of the anniversary conference of the 1845 flood, I was thrilled. That was hydrology in practice! In 2003, we met the renowned Prague archaeologist Ladislav Hrdli\u010dka at the conference City and Water. He helped us a lot with understanding the development of Prague\u2019s terrain. He also introduced me to his colleague Zvonim\u00edr Dragoun, a surveyor who worked in nature conservation, heritage preservation, and archaeology. Today I can hardly imagine my work without him. In Prague, the archaeologist who now comes closest to the issues of fluvial sediments and their dating is Jan Havrda. Over the past thirty years, Prague archaeology has made great progress, particularly in interpreting changes in floodplain areas that are of such interest to us \u2013 for example, the development of Mal\u00e1 Strana, Kampa, and Kl\u00e1rov, the evidence of terrain changes around the Klementinum, or the position of the old wooden bridge that was deeply submerged during the flood of 1118.<\/p>\n

\"\"<\/a>Photograph with a floodmark on a monastery in\u00a0Plasy showing that in\u00a01872 I would have had no chance at this spot.<\/h6>\n

We have received help from staff at Prague Museum and from many other museums and archives \u2013 in total, dozens of people. Our most substantial joint work, however, has been with the historian Jan Lhot\u00e1k, a specialist on the history of the \u0160umava region and the town of Su\u0161ice. In 2013 we published together an extensive collection on the floods of the Otava River from 1432 to 1900. We had hoped that a follow-up in book form would also find support, but to our surprise there was no interest. I believe that interdisciplinary collaboration is far more natural in Western Europe, though it is gradually gaining ground here as well. If I were to name people internationally who study the history of floods, I must mention the historian Andrea Kiss, who\u00a0works at the\u00a0Technische Universit\u00e4t (TU) Wien alongside the\u00a0hydrologist Professor G\u00fcnter Bl\u00f6schl. Within\u00a0the\u00a0community of\u00a0scholars dedicated to historical floods in\u00a0Europe, one finds archaeologists, historians, geographers, and geologists. This diversity is also evident at meetings and conferences, where the\u00a0\u201cbalance of\u00a0forces\u201d is strikingly varied.<\/p>\n

How can knowledge of\u00a0past extreme events help in\u00a0preparing for future floods in\u00a0the\u00a0context of\u00a0climate change?<\/span><\/h4>\n

Yes, it may seem illogical. Everything changes, so why look back to the\u00a0past? Yet the\u00a0climate has always changed to some degree. We can see this in\u00a0floods in\u00a0our region as well: during the\u00a0colder periods of\u00a0the\u00a0seventeenth and eighteenth centuries, large winter floods were more common, but from the\u00a0second half of\u00a0the\u00a0nineteenth century, summer floods prevail. In\u00a02019, together with Professor R\u00fcdiger Glaser from University of\u00a0Freiburg, I\u00a0stood in\u00a0Riederalp above the\u00a0Aletsch Glacier, where he pointed out the\u00a0\u201c1850\u00a0moraine\u201d. Since 1850 the\u00a0glacier has been retreating, and the\u00a0place where we stood just six years ago is now at risk of\u00a0landslides. Climate change and global warming may have consequences that are difficult to foresee today. But not everything changes. The\u00a0laws of\u00a0physics will remain\u00a0in\u00a0force, and the\u00a0morphology of\u00a0the\u00a0landscape, the\u00a0floodplains and river channels, as well as the\u00a0river network, are unlikely to undergo fundamental changes \u2013 at least not on the\u00a0time scale we are concerned with now.<\/p>\n

Even if the\u00a0atmosphere were to undergo very substantial changes, it is certain\u00a0that knowledge of\u00a0past extreme events will remain\u00a0useful. The\u00a0already mentioned classic figure of\u00a0historical flood research, Victor Baker, summed it up in\u00a0a\u00a0single sentence: \u201cWhat has happened once can happen again, because it is real.\u201d Indeed, floods that have actually occurred have one undeniable advantage over those merely modelled \u2013 they cannot be dismissed. However astonishing their parameters may sometimes appear, they must be accepted as fact.<\/p>\n

It is possible that future events may occur in\u00a0somewhat different ways \u2013 for example, with greater frequency. It is evident that in\u00a0the\u00a0past five centuries there have been several periods when floods were both more frequent and more intense. These often coincided with times when the\u00a0troposphere had been subjected to a\u00a0powerful impulse, such as after the\u00a0major volcanic eruptions in\u00a0Iceland and Japan in\u00a01783. In\u00a0the\u00a0period that followed, Europe experienced severe winters, devastating floods, and other anomalies.<\/p>\n

It is difficult to prove a\u00a0direct influence of\u00a0climate change, or global warming, on recent floods. The\u00a0outcome of\u00a0our efforts in\u00a0this regard was the\u00a0project led by Professor G. Bl\u00f6schl, which evaluated long historical series of\u00a0flood peaks, from 1500 to the\u00a0present. Our joint paper was published in\u00a0Nature. The\u00a0period 1993\u20132016 was assessed as the\u00a0second most intense in\u00a0terms of\u00a0flooding in\u00a0Europe since 1500. Is this evidence of\u00a0the\u00a0impacts of\u00a0climate change? For some, yes; for others, not yet.<\/p>\n

Throughout your scientific career, you\u2019ve worked with many experts, including our recently deceased colleague Ladislav Ka\u0161p\u00e1rek, a hydrologist at TGM WRI. Could you describe your collaboration with him and share a fond memory, please?<\/span><\/h4>\n

I\u00a0had probably known Ladislav Ka\u0161p\u00e1rek since around 1985 or 1986, during the\u00a0fifth year at CTU \u2013 so roughly forty years. He taught an optional course in\u00a0Hydrological Modelling as an external lecturer. It lasted just one semester. For my diploma thesis, I\u00a0was assigned the\u00a0task of\u00a0carrying out automatic optimization of\u00a0the\u00a0hydrological Tank Model using the\u00a0Rosenbrock method. The\u00a0thesis supervisor was Miroslav Kemel, and Ladislav Ka\u0161p\u00e1rek served as consultant. My task was not only to calibrate the\u00a0model based on a\u00a0historical event on the\u00a0Otava River, but also to describe the\u00a0very clever Rosenbrock optimization method. Yet even this method, capable of\u00a0efficiently searching in\u00a0a\u00a0multidimensional parameter space for the\u00a0optimum of\u00a0an objective function, often fell into the\u00a0trap of\u00a0local optima. It was a\u00a0good lesson in\u00a0the\u00a0importance of\u00a0staying \u201cdown to earth\u201d and applying logic and common sense alongside the\u00a0powerful mathematical apparatus. I\u00a0believe Ladislav Ka\u0161p\u00e1rek was a\u00a0real support in\u00a0this regard.<\/p>\n

After I\u00a0returned from military service in\u00a0September 1987, Ladislav Ka\u0161p\u00e1rek changed jobs and moved to TGM WRI. His position as head of\u00a0the\u00a0Department of\u00a0Regime Data Processing was taken over by Old\u0159ich Novick\u00fd. Yet traces of\u00a0Ladislav Ka\u0161p\u00e1rek\u2019s\u00a0work were everywhere \u2013 for example, in\u00a0his initiative to establish and organize the\u00a0hydrology photo archive together with the\u00a0meticulous technician Eva Ba\u0159inov\u00e1. The\u00a0photographs of\u00a0hydrological structures were arranged by type, and the\u00a0flood photographs chronologically. Ladislav Ka\u0161p\u00e1rek more than anyone else realized how essential such an archive would be. The\u00a0same applied to many other seemingly simple things. My cooperation with him continued even after he left the\u00a0Prague branch of\u00a0CHMI, whether it concerned artificially generated time series, methodologies for calculating water balance, or flood wave analyses. When my interests turned toward historical hydrology, I\u00a0found in\u00a0him clear support and understanding.<\/p>\n\"\"<\/a>\n

 <\/p>\n

A photograph of\u00a0Ladislav Ka\u0161p\u00e1rek acting as a scale figure, holding a rod above the\u00a01616\u00a0mark.<\/h6>\n

How did Ladislav Ka\u0161p\u00e1rek support you in\u00a0your work on historical hydrology?<\/span><\/h4>\n

Later, when I began my dissertation, he offered to collaborate on the evaluation of the 2002 flood, specifically in searching for historical parallels to that event. This form of cooperation continued further, also leading to co-authorship of IF articles. I prepared historical materials for various studies, including work on the Rakovnick\u00fd Stream. Very often, I simply asked him whether this or that was a good idea. To conclude, I would like to share a memory that contains neither a humorous punchline nor a hidden deeper\u00a0meaning. It is, however, a\u00a0memory that I\u00a0enjoy recalling in\u00a0my mind. It relates to the\u00a0catastrophic period of\u00a0drought. Hydrological drought began to manifest as early as 2014 and continued until spring 2020. Every cloud has a\u00a0silver lining: we had long awaited the\u00a0opportunity to observe the\u00a0hunger stone in\u00a0D\u011b\u010d\u00edn rise as much as possible above the\u00a0water. The\u00a0best chance to record all thirty markers of\u00a0minimum water levels on its surface came in\u00a0August 2015. After phone calls and some theoretical preparation, Ladislav Ka\u0161p\u00e1rek organised the\u00a0expedition. We travelled in\u00a0an off-road vehicle driven by Jan Ka\u0161p\u00e1rek, his son. Naturally, the\u00a0surveyor Zvonim\u00edr Dragoun, an indispensable collaborator, accompanied us. Excavating and cleaning the\u00a0stone is a\u00a0task for four people, taking roughly half a\u00a0day. Despite the\u00a0contribution of\u00a0the\u00a0Vltava cascade, the\u00a0water level had dropped very low, so all the\u00a0markers were clearly visible. That day \u2013 I\u00a0believe it was 14\u00a0August 2015 \u2013 the\u00a0afternoon temperatures in\u00a0D\u011b\u010d\u00edn reached around 38\u202f\u00b0C, yet Ladislav handled the\u00a0spade with great skill. By around three o\u2019clock, however, we had all had enough. The\u00a0stone was fully excavated and clean. At the\u00a0side, where the\u00a0famous inscription reads \u201cWenn du mich siehst, dann weine\u201d (\u201cIf you see me, weep,\u201d editorial note), something else appeared beneath the\u00a0water \u2013 perhaps a\u00a0five-pointed star. Was there a\u00a0marker somewhere beneath it as well? We could not go any deeper, unless the\u00a0outflow from the\u00a0St\u0159ekov weir was temporarily reduced. Calmly, Ladislav said, \u201cWell, let\u2019s\u00a0build a\u00a0little dam then.\u201d We quickly constructed a\u00a0small barrier around the\u00a0side of\u00a0the\u00a0stone. We removed the\u00a0water using a\u00a0plastic mineral water bottle and, I\u00a0believe, even a\u00a0pump originally intended for cleaning and rinsing the\u00a0stone. It was a\u00a0battle between seepage and the\u00a0pump\u2019s\u00a0capacity. Jan Ka\u0161p\u00e1rek shovelled gravel and mud tirelessly until the\u00a0job was done. In\u00a0the\u00a0process, he unearthed the\u00a0lowest marker from 1934. It turned out that the\u00a0measurements previously taken at the\u00a0gauge and the\u00a0heights of\u00a0the\u00a0markers matched almost exactly. The\u00a0difference between the\u00a0annual minimum recorded at the\u00a0gauge in\u00a01868 and the\u00a0corresponding marker was zero! We used the\u00a0same, slightly refined, method again\u00a0when scanning the\u00a0stone in\u00a02018.<\/p>\n

Which joint project or topic would you consider central to your collaboration?<\/span><\/h4>\n

If I\u00a0were to identify the\u00a0common thread of\u00a0our collaboration, it would almost certainly be the\u00a0flood of\u00a0May 1872. Since 1981, this flood never left Ladislav Ka\u0161p\u00e1rek\u2019s\u00a0mind; he returned to it again\u00a0and again. He initiated renewed work on the\u00a0topic in\u00a02000, which involved field surveys along the\u00a0St\u0159ela and Bl\u0161anka streams. Subsequent steps focused on more detailed information about damage to water mills and ponds, as well as using Aqualog for re-simulation. The\u00a0final step was the\u00a0estimation of\u00a0the\u00a0Rakovnick\u00fd Stream\u2019s\u00a0flow, culminating in\u00a0the\u00a0book on historical floods (Historical Floods on the\u00a0Rakovnick\u00fd Stream, editorial note). After the\u00a0joint lecture presenting this book on 18\u00a0March at TGM WRI, we spoke for another two hours in\u00a0the\u00a0office. Eventually, we went to his archive in\u00a0the\u00a0corridor and up to the\u00a0attic. He pointed out the\u00a0essential items that should be preserved. Sadly, this is now the\u00a0very last memory\u2026<\/p>\n

Dr Elleder, we sincerely thank you for the\u00a0interview and for providing the\u00a0photographs.<\/em><\/p>\n

Ing. Libor Elleder, Ph.D.<\/span><\/h3>\n

Ing. Libor Elleder, Ph.D., was born on 11\u00a0July 1963 in\u00a0Prague. He studied at the\u00a0Faculty of\u00a0Civil Engineering at Czech Technical University, specialising in\u00a0Hydraulic Structures and Water Management. He focused on hydrology, including his master\u2019s thesis on Automatic Optimisation of\u00a0a Hydrological Tank Model. After completing his studies, he joined the\u00a0Czech Hydrometeorological Institute. Until 1993, he worked in\u00a0the\u00a0Data Regime Processing Department, focusing on flood recurrence intervals calculations, generation of\u00a0synthetic series, and data processing in\u00a0unmonitored profiles, also serving as a programmer for a range of\u00a0tasks. From 1993 to 2013, he worked as a forecaster, specialising in\u00a0hydrological predictions. Since the\u00a01990s, he has also been engaged in\u00a0historical hydrology. In\u00a02009, he defended his doctoral dissertation at Charles University on The\u00a0Use of\u00a0Proxy Data in\u00a0Hydrology. Since 2013, he has worked in\u00a0the\u00a0Department of\u00a0Applied Hydrology, focusing on research. He has co-authored and authored numerous scientific articles, contributed to several professional books, and worked on an ArcGIS-based application for flood mapping. Currently, he is a member of\u00a0the\u00a0Floods Working Group Pages and collaborates with the\u00a0Working Group for the\u00a0History of\u00a0Hydrology.<\/p>\n","protected":false},"excerpt":{"rendered":"

Have you ever wondered what a hydrologist might discuss at a table with historians, archivists, and chroniclers? Can historical data help us gain a better understanding of today\u2019s flood risk assessment? And might deeper knowledge of past floods prepare us for future ones linked to climate change? We put these questions to Ing. Libor Elleder, Ph.D., in the October hydrology issue of VTEI.<\/p>\n","protected":false},"author":8,"featured_media":36449,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[2,86,93],"tags":[3935,3937,674,3936,2450],"coauthors":[124,2785],"class_list":["post-36726","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-from-the-world-of-water-management","category-hydraulics-hydrology-and-hydrogeology","category-two-articles","tag-archive-sources","tag-chronicles","tag-floods","tag-historical-sources","tag-hydrology"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36726","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/comments?post=36726"}],"version-history":[{"count":4,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36726\/revisions"}],"predecessor-version":[{"id":36730,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36726\/revisions\/36730"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media\/36449"}],"wp:attachment":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media?parent=36726"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/categories?post=36726"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/tags?post=36726"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/coauthors?post=36726"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}